ECU and fuel pump resistor

[Amon]

Top of the morning, SM. I've got two questions regarding my non-starting car, an MA70 turbo.

First is that I'm getting no spark, no fuel pressure, and my Check Engine Light is non-functioning. My first guess is that the ECU is knackered, but can anyone here confirm my suspicion? If so, what would cause the computer to die? It was functioning fine in the car it was pulled out of. I opened it up to check for popped resistors and caps and broken solders but I didn't see anything; are these little buggers repairable?

My second question is: is the fuel pump resistor necessary for operation? The car is using a Walbro 255 L/hr pump.

Cheers lads

 

[hvyman]

Yes you need the fuel pump resistor.

Do you have the grounds on the intake manifold?

 

[jetjock]

The resistor is necessary in the sense it either needs to be installed or bypassed if removed.

It's rare for a 7M ECU to fail. Possible but unlikely. Typical causes of no MIL would be bad wiring or a blown lamp. These are easily checked by measuring/grounding terminal W on the ECU. Or you could pull the cluster. Why anyone would go through all that just to check the lamp is beyond me but I've seen people do it.

A less typical cause is the 5 volt sensor power (Vc) being shorted to ground. In that case the ECU will be rendered dysfunctional and be unable to run the engine. Some of the places Vc can be checked at are the ECU, AFM, and TPS.

 

[Amon]

Yup the fuel pump resistor was bypassed by previous owner so I was curious about its necessity.

About the grounds: the intake manifold ground is good. I actually went around and verified as many 12v grounds as I could reach and they all checked out OK. I replaced the CEL lamp to no effect, but haven't verified the cluster or 5v circuits. I'm still suspicious about the ECU because I found online somewhere that my symptoms appear to match a dead ECU situation.

Cheers for the heads up.

 

[Nick M]

Yup the fuel pump resistor was bypassed by previous owner so I was curious about its necessity.

It makes the pump last longer.

 

[gottadiesel]

My second question is: is the fuel pump resistor necessary for operation? The car is using a Walbro 255 L/hr pump.

It makes the pump last longer.

Not to argue, as your statement is true, yet IMO depends on your setup as to whether it should or should not be installed, mine runs out of fuel (going lean past 14psi of boost and 4.5k) with resistor and stock fuel pump relay. I am not certain I guess, that they were working 100%, but I do know by bypassing the resistor and using the stock fp relay as pilot duty only and utilizing a new 20amp circuit, my fuel pressure and going lean issues went away... So I am just saying be aware if you are thinking of un-bypassing it, as it may change your AFRs.

 

[3p141592654]

The first thing I would do is confirm that there is 12V at the ECU BAT and IGSW pins with the key on. Your symptoms are consistent with no power to the ECU.

 

[Nick M]

Not to argue, as your statement is true, yet IMO depends on your setup as to whether it should or should not be installed, mine runs out of fuel (going lean past 14psi of boost and 4.5k) with resistor and stock fuel pump relay.

Well, I am certain. With a 57 T04E Boss Jr, I don't go lean at 14.5 psi unswitched. In fact, on the dyno, the ECU had did not flinch at keeping its 9.7-10.1:1 AFR. As already pointed out, you have some trouble shooting to do.